I can’t remember how I set it up, but I had this armature where I had a series of sub-master bones parented to characters limbs, bones that controlled both hands or both legs at once. When I scaled one of sub-master bones, it also scaled the child bones, but it only translated the vertices of the mesh they were parented to as to make the arms or legs spread outward or inward while maintaining their scale, it did not scale the mesh itself. In other words, there was a convenient way to use scaling to make symmetric translations.
How is this done?
In case anyone else has this question, I figured it out. You need to add an extra set of bones that each limb IK or control is parented to through the child constraint modifier, then turn off the scaling. I’ve uploaded an example with an animation to demonstrate a basic setup. Remember to turn off “Deform” in the Bone Properties menu near the bottom for all the bones that are simply scale/translation controls that are not intended to deform the mesh.